Researchers track moose decline

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The moose population in the area around the Cabinet Mountains and Fisher River south of Libby appears to have declined in recent decades. 

If you went hunting last year, the people at the check station who asked if you had seen any moose weren’t just making conversation.

Those drive-by surveys are part of an ongoing study by Montana Fish, Wildlife and Parks to find out why the massive ungulates have been disappearing from the landscape over the past few decades.

Jesse Newby, a wildlife research technician for Montana Fish, Wildlife and Parks, said the statewide study launched in 2013. He and wildlife biologist Nick DeCesare use aerial flights and radio tracking as their primary tools to monitor moose populations in the Cabinet Mountains, the Big Hole Valley and the Rocky Mountain Front.

“One of the things that came out is that we really didn’t know what the population was,” Newby said. “We also wanted to get a better understanding of that population data and what in the environment might be a limiting factor.”

As big game animals go, moose live a long time and are notoriously difficult to track down. In addition, their range and movements vary widely between individuals.

“There wasn’t, in any of these areas, a typical moose movement pattern throughout the year,” Newby said. “Each of them have a very different strategy, and for some of them it’s hard to see what that strategy is at all.”

That means the state’s dataset for mortalities is still small, so hunter surveys are helping fill in the gaps in the data. The researchers also rely on the historic record of tags sold and moose harvested over the years to confirm a drop throughout their range in the western part of the state.

After moose were nearly exterminated in Montana in the late 1800s due to over-harvesting, the state’s nearly 50-year ban on moose hunting allowed the overall population to rebound. In 1945, a limited hunt reopened when 90 tags were issued.

By 1962, the number of statewide permits hit an all-time high of 836, remaining in excess of 600 for all but a handful of years during the next three decades.

But since the mid-’90s, the number of available moose tags has dropped by more than 50 percent, and a successful moose hunt, on average, now requires significantly more effort.

In 2014, fish and game issued just 353 permits out of more than 26,000 applications. This year the agency issued 363 permits.

DeCesare, who leads the population study, said it appears to be part of a trend playing out across the northern reaches of the continental U.S.

“What we’re seeing with moose is sort of a consistent pattern of declines in these southern-edge states,” said.

In Minnesota, researchers have spent more than a decade trying to pin down the cause behind a dramatic decline during the 1980s and 1990s. In just 10 years, one of its two distinct moose populations dropped to nearly zero. Biologists in Maine and New Hampshire have documented similar trends.

The waning presence of moose has been less severe in Montana, but DeCesare estimates the total population in the Treasure State is about half of what it was as recently as the ’90s.

Disease is one of several factors potentially driving the disappearance of moose, and the effects of climate change could be further compounding the problem.

Pointing to research in Minnesota and Maine, DeCesare believes that the long-term warming trend is at least partially responsible for the decline.

A pair of studies of Minnesota moose, published in 2009 and 2010, linked mortality to heat stress, and a 2006 study found that population growth decreased alongside increases in average summer temperatures.

Moose are adapted to live in boreal forest, a habitat characterized by cold, snowy winters that extends from Canada and Alaska into portions of the lower 48 states. But according to DeCesare, a long-term warming trend in the region could be pushing the animals farther north.

During a conference call to discuss “Game Changers,” a new report by the National Wildlife Federation on climate change’s impact on game species, he said biologists have two theories on how rising temperatures could be impacting moose populations.

“One is direct heat stress,” DeCesare explained. “Once you go to about 30 degrees in the winter or to 60 or 70 degrees in the summer, they suddenly start having to work a lot harder to be a moose.”

The other is tied to a separate theory: parasites. That notably includes winter ticks, of which more than 70,000 have been found on a single animal. New England researchers have linked much of the decline in that region to an increase in winter ticks, which thrive during warmer winters and earlier snowmelt.

“What makes good winter tick conditions are open springs,” said Newby. “If there’s a lot of snow on the ground in April when they drop off, you don’t get a lot of them surviving. But when the ground is brown by April, that’s really ideal.”

Preliminary data from the Cabinet population — historically a moose stronghold — have been encouraging, but Newby noted that pulling a consistent trend from the numbers will take more time.

“It’s three years of data so it probably doesn’t mean much,” he said. “But there’s a possibility that there was a decline and we are looking at it post-decline right now.”

While the average number of calves per cow moose appeared to be low, he said enough cows are surviving each year that the population seems to be increasing.

A relatively new population of moose along the Rocky Mountain Front also appears to be making strides.

“We had really good adult female survival, but for the first couple years it didn’t seem to have much calf production,” Newby said. “But then this last year hit and we had more cows than calves.”

On the border of Yellowstone National Park, however, data for moose in the Big Hole Valley appear to indicate the opposite. Calving rates are higher but female survival is much lower.

“In Big Hole, almost all [mortalities] have been the animals just tipping over. We’ve primarily classified it as some sort of pathogen, some sort of disease, but we’re not yet sure what it is,” Newby said. “If the mortality keeps at the pace it’s been going, it’s not going to be sustainable.”

The moose population study costs roughly $133,000 per year. Federal money from the sale of guns and ammunition covers the bulk of it, with the state required to chip in a $33,000 match. That comes from “governor’s tag” sales, in which the state auctions off a single moose tag each year that can be used anywhere in the state.

Newby said the value that hunters place on moose was a primary driver in getting the study off the ground. With more accurate data on the animals, wildlife managers can establish more reasonable hunting quotas and respond better to other causes driving the declines.

But he added that their importance reaches well beyond Montana’s hunting community.

“People just like moose. They’re kind of these iconic northern species,” he said. “If you live in a place with moose, it kind of identifies that place for you.”


Reporter Sam Wilson can be reached at 758-4407 or by email at swilson@dailyinterlake.com.

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